Process for depth-hardening of long tubes or the like



May 26, 1959 F. HEINENBERG PROCESS FOR DEPTH-HARDENING OF' LONG TUBES QR THE LIKE Filed lMay 17, 1955 erg United States Patent O PROCESS FOR DEPTH-HARDENING OF LONG TUBES OR THE LIKE Fritz Heinenberg, Dusseldorf, Germany, assignor to Mannesmann Aktiengesellschaft, Dusseldorf, Germany, a German company Application May 17, 1955, Serial No. 508,876

2 Claims. (Cl. 14S-21.55)

This invention is for improvements in or relating to a process and apparatus for hardening long tubes or other hollow bodies on the inner side thereof. One field to which the present invention has been found to be especially applicable is that of tubes employed in oil-fields. Oil-field tubes, such, for example, as pipe liners, have in the last few years been coming into increasing use for petroleum bores of relatively great depth, and the requirements as to the strength of such tubes are increasing accordingly. Alloy steels were first used as the tube material and efforts were then made to bring unalloyed carbon steel tubes to the desired strength value by heat treatment, consisting of chilling the heated tubes from the hardening temperature by spraying water and by subsequent drawing treatment. However, the tubes became distorted during the chilling step and became relatively oval, therefore being rendered unsuitable as pipe liners and all efforts to obviate distortion and ovality of the tubes have been unsuccessful.

According to the invention, however, it is possible to obviate these defects and provide very rapid manufacture if the cooling liquid, such, for example, as water or oil or an oil emulsion, can be made to pass along the inner surface of the tube at great speed following a helical path. This step can be carried out in a simple manner if there is fitted to one end of the tube, which is heated to hardening temperatures, a discharge nozzle from which the cooling liquid issues, having had the swirling motion of a vortex imparted thereto, and flows along the tube to be cooled in a helical path.

According to the present invention, there is provided a process for depthdhardening long tubes or the like from the inside, wherein a coolant passes in the manner of a vortex or helically along the inner surface of the tube at great speed.

Further, according to the present invention there is provided an apparatus for carrying out the process of the present invention comprising a coolant propulsion means, a discharge nozzle and coolant storage means.

The present invention will now be more particularly described with reference to the accompanying drawing which illustrates diagrammatically one method of carrying the present invention into effect. l

Referring to the drawing, there is illustrated a tube 1 which is rst heated in conventional manner in a continuous heating or tempering furnace 2 and, if desired, the said tube can be inductively heated. The tube 1 is then extracted from the furnace and brought to a roll table.

The tube 1 is pressed against the aperture of a discharge nozzle 4 and is held firmly in that position by means of clamping means 3. 'I'he discharge nozzle 4 contains spiral tins 4a to induce spiral whirling and the aperture 4b to add to the speed and etectiveness of the ,l CC

vortex. A pump 5 of approprlate capacity then forces a high-speed jet of coolant in the manner of a vortex along the inner surface of the tube 1 and the said coolant continues to travel in this manner until reaching the open end of the tube, whereupon the coolant is conveyed by way of intercepting means 6 to a collecting tank 7. The :chilling step is effected uniformly, with cooling of this kind, over the entire cross-section, and also over the whole length of the tube which may be of the order of, for example, 13 metres and more, in a few seconds. The tubes 1 were found to remain substantially straight and to retain their circular form, and not only were high impact test values obtained but also a considerable increase was noted in fatigue strength as compared' with conventional chilling in water or chilling by spraying. The intercepting means 6 takes the form of a pipe of diameter larger than that of the tube to be hardened and provided with an elbow therein.

Furthermore, the process described is suitable for hardening tubes up to about 250 mm. diameter. If, however, tubes or hollow bodies are to be hardened which have a greater internal diameter but it is not desired to increase pump capacity excessively, a core can be slid into the tube or hollow body, the said core being of such dimensions that an annular space about 2 or 3 cm. remains between the tube or hollow lbody to be hardened and the core. In the case under consideration, the discharge nozzle is formed as an annular nozzle and the jet of coolant is forced in the manner of a vortex through the annular space between the tube and the core. In every case coolant speed is determined by the selected pressure and by discharge nozzle dimensions and these are so chosen that the helical course of the coolant jet inside the tube to be cooled is reliably maintained until the jet reaches the exit end of the tube.

The coolant herein'before referred to may be water, oil, oil emulsion or the like according to circumstances.

What l claim as my invention and desire to secure by Letters Patent of the United States is:

1. A process for the depth hardening of long tubes from the inside by means of a cooling liquid, characterized in that the tube is left in a horizontal position as it comes from the manufacturing operation and the cooling liquid is introduced into the tube at an open end in a vortical manner with a horizontal axis and at suiiicient speed and pressure so that the coolant ows inba vertical manner throughout the entire length of the tu e.

2. A process as claimed in claim 1 for hardening tubes of large internal diameter, wherein there is introduced into the tube to be hardened a core of such external diameter that there remains between the tube to be hardcned and the core an unobstructed annular space through which the coolant can pass in the manner of a vortex or helically.

References Cited in the le of this patent UNITED STATES PATENTS 1,513,974 Ehn Nov. 4, 1924 1,893,979 Barrere Jan. 10, 1933 2,169,555 Carruthers Aug. 15, 1939 2,239,796 Stratton Apr. 29, 1941 2,545,028 Haldeman Mar. 13, 1951 FOREIGN PATENTS 371,080 Great Britain Apr. 21, 1932 682,777 Great Britain Nov. 19, 1952 

1. A PROCESS FOR THE DEPTH HARDENING OF LONG TUBES FROM THE INSIDE OF A COOLING LIQUID, CHARACTERIZED IN THAT THE TUBE IS LEFT IN A HORIZONTAL POSITION AS IT COMES FROM THE MANUFACTURING OPERATION AND THE COOLING LIQUID IS INTRODUCED INTO THE TUBE AT AN OPEN 